Hybrid vehicles may include an engine and an electric machine. The electric machine may provide positive torque to accelerate the vehicle or negative torque and charge to an energy storage device in a regeneration mode. If the electric machine is operating in a regeneration mode and the driver requests positive driveline torque via the accelerator pedal, torque in the driveline may reverse causing impact between gear teeth in the driveline. The impact may result from spacing between gears in the driveline, and the noise produced by impact between gear teeth may be objectionable to a driver.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for controlling driveline lash, comprising: shifting a transmission to a gear that permits an electric machine that is coupled to the transmission to operate at a lower speed than a base speed of the electric machine in response to a decrease in a driver demand torque; and reducing gear tooth to gear tooth impact via operating the electric machine in a speed control mode during a driveline torque transition from a negative torque to a positive torque.
By operating an electric machine of a vehicle driveline in a speed control mode, it may be possible to reduce gear tooth to gear tooth impact that is related to gear lash. For example, an electric machine operated in a speed control mode may manage torque flow through a torque converter so that impact between gear teeth may be reduced. Additionally, the transmission may be operated such that speed of the electric machine is maintained below or operated near a base speed of the electric machine where torque from the electric machine is a maximum value. Consequently, if lash compensation is desired, the electric machine can apply full torque to mitigate gear tooth impact.
The present description may provide several advantages. Specifically, the approach may reduce gear tooth impact, thereby extending gear life. Further, the approach may improve vehicle drivability and reduce drivetrain noise.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.